It has been a bad week all around cake wise but this one I don't even know what the problem is. Nothing is different with my recipies or routines (no frozen cake, returned crumb coated cake to fridge for a few hours before final coat) Anyway, when adding the MMF decorations I started to see what I thought was an air bubble forming I poked it with a tooth pick and all was better. then a bit later a crack had formed at the top corner and the frosting (including crumb coat was literally peeling away from the cake. Gravity was not a friend to the shape of this cake and that may be the only cause but there it only got worse when I delivered it. It is a square whimsical tapered bottom cake. Fixing it on site was a nightmare. (Luckily it is a wonderful repeat customer that smiled graciously) but oh my goodness. I ended up taking off a corner of the top tier and leaving her extra fondant dots and ribbons that she could use to cover up more if needed in the morning. I did not have my camera for during or after photos. HELP...what causes it and how do I prevent it from happening again? Last week I had an unusual air bubble under my fondant too but now I am wondering if the frosting was peeling off and bulging out versus an air bubble? Crying is all I can do at this point. So frustrated and defeated.

I m sorry u had this problem. I had a similar problem w a cake I made for a client that she picked up yersterday. I used Betty crocker s vanilla frosting to cover it and all it kept doing was melting. I sure was praying hard and was feeling like crying too. I d also like to know why your cake did that if u used the same recipe and followed the exact same routines.

Not an expert but seems like it would have something to do with the moisture level in the cake. Could it have to do with temperature of ingredients used? I would be crying too. Anxious to hear what more experienced bakers have to say.

Had to refrost the top tier of a wedding cake on site because the exact thing happened. Would really like to have an answer too. Have been at this for six years and am all the sudden having this problem.

It sounds to me like the recipe for icing as too dry - not creamy. I'm not talking about the icing needing more liquid to thin the consistency but using more 'fat' vs. sugar for a creamy texture.
Most/ many times bubbles form because one is not putting enough pressure on the icing to get a good seal to the cake which allows for trapped air causing a 'blowout' when covering a cake w/fondant. Some people have suggested that after a cake is covered, take a pin and poke holes every couple of inches all around the base of the cake. The bottom boarder will cover them.
Personally I found once I used a fondant smoother most of that problem stopped. I had been using my hands to smooth the fondant on the cake. W/a fondant smoother I was probably spending a bit more time and put more pressure on the fondant to adhere it to the cake better.

Thank you Kakeladi for your reply. I will look at adding more fat to the frosting and this particular cake was not covered in fondant perhaps I did not apply enough pressure when frosting it as I normally would add lots of pressure when applying the fondant which did not happen. HMMM? I have been doing this for a few years with no problem so hopefully this was just a fluke! Thanks for your idea about the holes at the bottom of the cake too. I have never heard of that one for fondant covered cakes.

I am pretty sure it has something to do with the temp. Cold cake and warm frosting. A gas forms as it comes and sometimes causes the blowout or peeling of frosting. I have had it happen too and it doesn't show up usually til later. Urgh Good luck! There are other posts about this you can look up! If you chilled your cake w/crumb coat for several hours that may be the problem.

humidity was the problem for me this week!! every cake gave me a fit!!!